Human Anatomy and Physiology: Unit 3 Endocrine, Blood, Cardiovascular, and Lymphatic Systems

Comprehensive vocabulary flashcards covering the anatomy and physiology of the Endocrine, Blood, Cardiovascular, and Lymphatic systems.

Hormones

Chemical substances secreted by endocrine cells into extracellular fluids that regulate the metabolic activity of other body cells.

Target Cells / Organs

Specific body tissues or organs possessing specific protein receptors that bind to a particular circulating hormone to trigger a cellular response.

Direct Gene Activation

The six-step mechanism used by lipid-soluble steroid hormones where the hormone diffuses across the plasma membrane, enters the nucleus, binds a specific receptor, attaches to cell DNA, transcribes mRNA, and directs new protein synthesis.

Second Messenger System

A four-step signaling mechanism utilized by water-soluble protein and peptide hormones, wherein the hormone binds a membrane receptor, activates an enzyme, produces second messenger molecules, and triggers intracellular changes.

Hormonal Stimuli

An endocrine release mechanism in which endocrine glands are prodded into action by other hormones, typically regulated rhythmically by negative feedback.

Humoral Stimuli

The control of hormone release elicited directly by changing blood levels of certain critical ions and nutrients, such as low blood $Ca^{2+}$ prompting parathyroid hormone release.

Neural Stimuli

The activation of endocrine secretion by direct nerve fiber impulses, such as preganglionic sympathetic fibers triggering catecholamine release from the adrenal medulla during stress.

Endocrine Glands

Ductless glands that synthesize and secrete hormones directly into the blood or extracellular fluid.

Oxytocin

A hypothalamic hormone stored in the posterior pituitary that stimulates powerful contractions of the uterine muscle during childbirth and causes milk ejection during nursing.

Antidiuretic Hormone (ADH)

A hormone produced by the hypothalamus and stored in the posterior pituitary that prevents urine production by causing kidneys to reabsorb water, increasing blood volume and raising blood pressure in large amounts.

Tropic Hormones

Hormones produced by the anterior pituitary that target other endocrine glands and stimulate them to secrete their own hormones.

Growth Hormone (GH)

A general metabolic protein hormone from the anterior pituitary that directs muscle and long-bone growth, stimulates amino acid uptake into proteins, and breaks down fats for energy while sparing glucose.

Prolactin (PRL)

An anterior pituitary hormone whose only confirmed human target is the breast, where it stimulates and maintains milk production after childbirth.

Follicle-Stimulating Hormone (FSH)

A gonadotropic hormone that stimulates ovarian follicle development in women and sperm development in the testes in men.

Luteinizing Hormone (LH)

A gonadotropic hormone that triggers ovulation and progesterone production in women, and stimulates testosterone production in men.

Melatonin

A hormone secreted by the pineal gland with peak levels at night and lowest levels midday, functioning as a sleep trigger that influences the body's circadian rhythm.

Thyroid Hormone

The major metabolic hormone consisting of thyroxine ($T_4$) and triiodothyronine ($T_3$), responsible for controlling the rate of glucose oxidation into energy and supporting tissue growth.

Calcitonin

A hormone made by the parafollicular cells of the thyroid that decreases blood calcium levels by depositing $Ca^{2+}$ into bones, acting antagonistically to parathyroid hormone.

Parathyroid Hormone (PTH)

The primary regulator of blood calcium homeostasis, released by the parathyroid glands when blood $Ca^{2+}$ drops to stimulate bone destruction and kidney/intestinal calcium absorption.

Thymosin

A hormone produced by the thymus gland that is essential for the normal development of T lymphocytes.

Adrenal Glands

Paired glands located superior to the kidneys, consisting of an outer glandular cortex divided into zones (zona glomerulosa, fasciculata, reticularis) and an inner neural medulla.

Aldosterone

The primary mineralocorticoid produced by the outermost adrenal cortex that regulates blood sodium and potassium ions by prompting kidney tubules to reabsorb $Na^+$ and secrete $K^+$.

Glucocorticoids

Adrenal cortex hormones, including cortisone and cortisol, that raise blood glucose by breaking down fats and proteins, help resist long-term stressors, and decrease edema to reduce inflammation.

Catecholamines

Epinephrine and norepinephrine secreted by the adrenal medulla that trigger the alarm stage of the fight-or-flight response, increasing heart rate, blood pressure, blood glucose, and dilating airways.

Pancreatic Islets

Endocrine clusters (islets of Langerhans) scattered within the exocrine pancreas that produce insulin from beta cells and glucagon from alpha cells.

Insulin

The only hormone that decreases blood glucose levels; secreted by pancreatic beta cells to enable body cells to import and oxidize glucose or store it as glycogen and fat.

Glucagon

A hyperglycemic hormone released by pancreatic alpha cells in response to low blood glucose that stimulates the liver to break down stored glycogen into glucose.

Buffy Coat

The thin whitish layer at the junction between erythrocytes and plasma in centrifuged blood, containing leukocytes and platelets and making up less than $1\%$ of total blood volume.

Albumin

The most abundant plasma protein synthesized by the liver; acts as a molecular carrier, an important blood buffer, and a contributor to the osmotic pressure of blood.

Erythrocytes

Anucleate, biconcave disc blood cells lacking most organelles that ferry oxygen using hemoglobin, normally presenting at $12\text{--}18\,g/100\,ml$ of blood.

Diapedesis

The process by which white blood cells slip in and out of intact blood vessels to enter tissue spaces.

Positive Chemotaxis

The directed movement of white blood cells through tissue spaces toward areas of tissue damage or infection in response to diffusing chemical signals.

Granulocytes

Leukocyte types with visible stained cytoplasmic granules and lobed nuclei, including neutrophils, eosinophils, and basophils.

Neutrophils

The most abundant white blood cells, featuring multilobed nuclei and fine granules, which act as active phagocytes during acute bacterial and fungal infections.

Eosinophils

Granulocytes with blue-red, earmuff-shaped nuclei that increase rapidly during parasitic worm infections to coat and digest parasites with granules.

Basophils

The rarest white blood cells, characterized by large granules containing histamine that make blood vessels leaky and recruit other leukocytes to inflammatory sites.

Agranulocytes

Leukocytes that lack visible cytoplasmic granules, featuring spherical or kidney-shaped nuclei; comprises lymphocytes and monocytes.

Monocytes

The largest circulating white blood cells with U-shaped nuclei that migrate into tissues to become macrophages and fight chronic infections.

Platelets

Irregularly shaped, anucleate cell fragments pinched off from multinucleated megakaryocytes in red bone marrow, critical for blood clotting with normal counts around $300{,}000\,\text{cells/mm}^3$.

Hematopoiesis

Blood cell formation that occurs in red bone marrow, producing roughly $100\text{ billion}$ new cells daily in the adult pelvic girdle, pectoral girdle, and proximal humerus/femur.

Erythropoietin

A hormone produced primarily by the kidneys in response to declining blood oxygen levels that targets red bone marrow to accelerate erythrocyte production.

Hemostasis

A fast, localized physiological response to stop bleeding from injured blood vessels, comprising vascular spasms, platelet plug formation, and blood coagulation.

Coagulation

The clotting cascade wherein tissue factor and platelet factor 3 interact with calcium ions to form thrombin, which converts soluble fibrinogen into an insoluble fibrin mesh that traps red blood cells.

ABO Blood Groups

Human blood classification determined by inherited surface antigens: type A has A antigens and anti-B antibodies, type B has B antigens and anti-A antibodies, type AB has both antigens and no antibodies, and type O lacks antigens and has both anti-A and anti-B antibodies.

Agglutination

The clumping of red blood cells caused by antibodies binding to foreign surface antigens, which can lead to clogged small vessels and hemolytic transfusion reactions.

Pericardium

A double-walled sac enclosing the heart made of an outer fibrous pericardium and a two-layered serous pericardium (parietal and visceral/epicardium layers) enclosing lubricating serous fluid.

Myocardium

The thick middle layer of the heart wall composed of whorled cardiac muscle bundles reinforced by dense fibrous connective tissue that contracts to pump blood.

Endocardium

The thin, glistening sheet of endothelium lining the heart chambers that is continuous with the inner endothelial linings of the major blood vessels.

Atria

The two superior, primarily receiving chambers of the heart that collect incoming blood and assist in filling the ventricles.

Ventricles

The two thick-walled, muscular inferior chambers of the heart that contract forcefully to pump blood out into pulmonary and systemic circulation.

Pulmonary Circuit

The pathway of blood from the right ventricle through the pulmonary trunk and arteries to the lungs for gas exchange, returning oxygenated blood via pulmonary veins into the left atrium.

Systemic Circuit

The vascular pathway where oxygen-rich blood is pumped from the left ventricle through the aorta to all body tissues, returning deoxygenated blood to the right atrium via the venae cavae.

Atrioventricular (AV) Valves

Valves positioned between atria and ventricles (bicuspid/mitral on the left, tricuspid on the right) anchored by chordae tendineae to prevent backflow into the atria during ventricular contraction.

Semilunar Valves

Three-cusped valves guarding the exits of the ventricles (pulmonary valve and aortic valve) that open during ventricular systole and close during diastole to prevent arterial backflow.

Intrinsic Conduction System

A built-in nodal network of specialized cardiac tissue that sets the basic rhythm of contraction and coordinates wave-like depolarizations from atria to ventricles.

Sinoatrial (SA) Node

The heart's natural pacemaker located in the right atrium that initiates depolarization waves and establishes the rhythm of each heartbeat.

Cardiac Cycle

The sequence of pressure and mechanical events during one complete heartbeat, comprising atrial systole, isovolumetric contraction, ventricular ejection, isovolumetric relaxation, and ventricular filling.

Cardiac Output

The volume of blood pumped out by each ventricle in $1\,\text{minute}$, calculated by the equation $CO = HR \times SV$.

Stroke Volume

The volume of blood pumped out of each ventricle with each individual heartbeat, determined primarily by the degree of cardiac muscle stretch and venous return.

Tunica Media

The bulky middle coat of blood vessels composed of smooth muscle and elastic fibers, controlled by sympathetic nerves to regulate vessel diameter and thicker in arteries than veins.

Brachiocephalic Trunk

The first major branch arising from the aortic arch, which bifurcates into the right common carotid artery and the right subclavian artery.

Hepatic Portal Circulation

A specialized venous system that directs nutrient- and toxin-rich venous blood from digestive organs, spleen, and pancreas through the hepatic portal vein into the liver before entering systemic veins.

Arterial Pulse

The alternating expansion and recoil of an artery that occurs with each contraction of the left ventricle, averaging $70\text{--}76\,\text{BPM}$ at rest.

Systolic Pressure

The pressure peak exerted inside systemic arteries at the moment of maximal ventricular contraction.

Diastolic Pressure

The baseline blood pressure maintained inside arteries while the ventricles are relaxing.

Lymph

Excess interstitial fluid containing leaked proteins, microbes, and cellular debris that has entered lymphatic capillaries to be returned to the bloodstream.

Lymph Nodes

Kidney-shaped lymphoid filter organs clustered along lymphatic vessels that house macrophages to engulf debris and bacteria and lymphocytes to mount immune defenses.

Spleen

A soft lymphoid organ in the left abdominal cavity that cleanses blood of foreign debris, recycles aged erythrocytes, stores platelets, and serves as a blood reservoir.

Tonsils

Small masses of lymphoid tissue located deep to the pharyngeal mucosa that trap and destroy airborne or ingested pathogens entering the throat.

Peyer's Patches

Clusters of lymphoid follicles located in the wall of the distal small intestine that destroy bacteria and prevent entry through the intestinal wall.

Acid Mantle

The acidic film formed by sweat and sebum on epidermal surfaces that inhibits surface bacterial colonization and growth.

Lysozyme

A protective antibacterial enzyme found in lacrimal secretions (tears) and saliva that breaks down microbial cell walls.

Natural Killer (NK) Cells

Nonspecific cytotoxic lymphocytes of the innate defense system that lyse and destroy virus-infected and cancerous cells directly without requiring antigen recognition.

Inflammatory Response

A localized innate secondary defense triggered by tissue injury that prevents pathogen spread, attracts phagocytes via chemical mediators, and promotes tissue repair.

Complement

A group of circulating plasma proteins that lyse microorganisms, promote phagocytosis through opsonization, and intensify the inflammatory response.

Interferons

Antimicrobial proteins released by virus-infected cells that bind to nearby uninfected cells to prevent viral replication and mobilize the immune system.

Pyrogens

Chemical substances released by leukocytes and macrophages that act on the hypothalamus to elevate body temperature and trigger fever.

Humoral Immunity

Antibody-mediated adaptive immunity provided by antibodies circulating in bodily fluids, produced by plasma cell descendants of sensitized B lymphocytes.

Cell-Mediated Immunity

Adaptive defense in which T lymphocytes directly lyse pathogen-infected cells or release cytokines to activate other immune cells after double-recognition of presented antigens.

Clonal Selection

The process where an antigen binds to a specific B lymphocyte receptor, stimulating the cell to proliferate into an identical army of plasma cells and memory cells.

Active Humoral Immunity

Long-term immunity acquired naturally from direct infection or artificially from vaccines, stimulating B cells to produce antibodies and establish immunological memory.

Passive Humoral Immunity

Short-lived immunity conferred by receiving preformed antibodies from a donor (e.g., via the placenta, breast milk, or antivenom) without engaging B cells or developing memory.

Cytotoxic T Cells

Effector T lymphocytes that kill foreign or infected cells directly by binding tightly and releasing toxic chemicals that form membrane pores, allowing fatal enzyme entry.

Helper T Cells

Regulatory T cells that orchestrate the adaptive immune response by releasing cytokines that stimulate B cell and cytotoxic T cell division while recruiting macrophages.

Regulatory T Cells

Specialized T lymphocytes that secrete chemicals to suppress B and T cell activity, halting the immune response once an infection is cleared.

Gastrin

A gastrointestinal hormone released by gastric mucosal cells in response to food ingestion that stimulates stomach parietal cells to secrete hydrochloric acid ($HCl$) and enhances gastric motility.

Ghrelin

A fast-acting peptide hormone secreted primarily by mucosal cells of an empty stomach that acts on the hypothalamus to stimulate appetite and promote food intake.

Arterial Pulse Pressure Points

Superficial anatomical locations where systemic arteries lie close to the body surface and can be compressed against bone to measure heart rate or stem hemorrhage, including nine primary clinical sites from the head to the feet.

Superficial Temporal Artery Pulse Point

The cranial pressure point palpated immediately anterior to the ear and superior to the zygomatic process of the temporal bone.

Facial Artery Pulse Point

The facial pressure point palpated along the lower margin of the mandible, approximately midway along the jawline anterior to the masseter muscle.

Common Carotid Artery Pulse Point

The major cervical pressure point palpated on the anterior and lateral neck, medial to the sternocleidomastoid muscle and lateral to the trachea.

Brachial Artery Pulse Point

The arm pressure point palpated along the medial bicipital groove and within the antecubital fossa medial to the biceps brachii tendon, routinely used for blood pressure auscultation.

Radial Artery Pulse Point

The most common clinical pulse site, palpated on the anterior lateral surface of the distal forearm/wrist, just proximal to the base of the thumb.

Femoral Artery Pulse Point

The groin pressure point palpated along the inguinal crease, midway between the pubic tubercle and the anterior superior iliac spine.

Popliteal Artery Pulse Point

The deep lower limb pressure point palpated behind the partially flexed knee joint in the center of the popliteal fossa.

Posterior Tibial Artery Pulse Point

The ankle pressure point palpated on the medial side of the lower leg, just posterior and inferior to the medial malleolus.

Dorsalis Pedis Artery Pulse Point

The pedal pressure point palpated on the superior/dorsal surface of the foot, running lateral to the extensor hallucis longus tendon.

Sinoatrial (SA) Node

A specialized mass of conducting cardiac tissue located in the right atrium that functions as the natural pacemaker of the heart, initiating depolarization impulses to establish the intrinsic rhythm of each heartbeat.

Lymphocytes

The second most abundant type of leukocyte, characterized by a large, dark spherical nucleus occupying most of the cell volume, which primarily resides in lymphoid tissues and plays a central role in adaptive immune defenses.

Aorta

The largest systemic artery of the body, emerging directly from the left ventricle to distribute oxygenated blood to the entire body.